Migrate to nullsatefy and Dio 4#84

Merged

franticn merged 7 commits intohurshi:masterfrom

vrtdev:feature/nullsafety-dio4

Apr 21, 2021

Commits on Mar 30, 2021

Fix regression in Dio 4 update where response interceptors were not called if from cache
erickok
committed

Commits on Apr 2, 2021

Fix regression where baseUrl was made non-nullable
erickok
committed

Commits on Apr 20, 2021

Fix cache handing upon an error response, which was not calling through the handler chain
erickok
committed